What kind of secretion is performed by meibomian glands?

Meibomian glands are specialized sebaceous glands located in the eyelids that play a crucial role in maintaining the health of the tear film. Their secretion is classified as holocrine, which is characterized by the entire glandular cell being destroyed in the process of secretion. In holocrine secretion, the cells within the gland undergo a series of changes that culminate in the release of their entire content, including cellular components, which then contribute to the oily layer of the tear film.

This type of secretion allows for the continuous replenishment of the lipid layer that prevents evaporation of the aqueous component of tears. The lipids produced by the meibomian glands help maintain the stability of the tear film and protect the ocular surface from desiccation.

While the other classifications of secretion—apocrine, merocrine, and exocrine—are notable in various biological contexts, they do not accurately describe the method by which meibomian glands excrete their lipid-rich secretion. Apocrine glands, for instance, lose only a portion of their cytoplasm during secretion, while merocrine glands release their products through exocytosis without cell damage. Exocrine is a broader term that encompasses glands that secrete their products